The present invention relates to a valve timing control system for an internal combustion engine, which controls an opening and closing timing of an intake valve and/or an exhaust valve in accordance with engine operating conditions.
Typically, the valve timing control system comprises a hydraulic phase adjusting mechanism accommodated in a housing and for changing the phase of rotation of a crankshaft and a camshaft, wherein supply/discharge of hydraulic fluid to/from the phase adjusting mechanism is carried out through a supply/discharge rod arranged through a cover member of the housing.
Specifically, the housing comprises a main body having a concave space and a cover member connected thereto so as to close the concave space. A through hole is formed in the center of the cover member to receive the non-rotatable supply/discharge rod. A seal ring having a spring force acting in the diameter increasing direction is engaged with the outer peripheral surface of the supply/discharge rod to hermetically seal a clearance between a front end of the supply/discharge rod and the phase adjusting mechanism by the seal ring. A taper surface is formed on the peripheral surface of the through hole of the cover member to increase the diameter of the through hole toward the outside of the housing, so that when inserting the supply/discharge rod into the through hole, the seal ring can easily be reduced in diameter along the taper surface.
With the typical valve timing control system, however, the cover member includes a flat plate member, so that if an attempt is made to enhance the insertion-ability of the seal ring by inclining the taper surface of the through hole in the direction to approach the axis of rotation, the cover member should be increased in thickness, which raises inconveniences such as increased weight of the entire system and lowered yield of materials.
It is, therefore, an object of the present invention to provide a valve timing control system for an internal combustion engine, which allows enhancement in the insertion workability of the seal ring without occurrence of increased weight of the entire system and lowered yield of materials.
The present invention provides generally a system for controlling a valve timing in an internal combustion engine, which comprises: a housing comprising a main body having a concave space and a cover member mounted to the main body to close the space, the cover member being formed with a through hole; a phase adjusting mechanism accommodated in the housing, the phase adjusting mechanism hydraulically changing a rotation phase of a crankshaft and a camshaft; a supply and discharge rod arranged through the through hole of the cover member, the supply and discharge rod being connected to the phase adjusting mechanism, the supply and discharge rod failing to be rotatable; a seal ring externally engaged with the supply and discharge rod, the seal ring hermetically sealing a clearance between the supply and discharge rod and the phase adjusting mechanism; a taper surface formed on a periphery of the through hole of the cover member, the taper surface increasing a diameter of the through hole toward the outside of the housing; and a protrusion formed with the cover member in a radially inside area thereof, the protrusion protruding in an axial direction of the system, the through hole being formed at the protrusion.